Rectifier control system



Aug. 28, 1934. E. KOBEL 1,971,720

RECTIFIER CONTROL SYSTEM Filed Dec. 27, 1932 INS UL A T/ON INSULAT/U/V- 22 a g g illi" Patented Aug. 28, 1934 UNITED STATES RECTIFIER CONTROL SYSTEM I Ernst Kobel, Ennetbaden,

to Aktiengesellsehaft Switzerland, assignor Brown Boveri & Cie.,

Baden, Switzerland, a joint-stock company of Switzerland 15 Claims.

This invention relates to improvements in rectifier control systems and more particularly to means for controlling the moment at which the anodes of an electron discharge device of the 5 gaseous or of the vapor type start carrying current to the potential of the cathode.

during each cycle of the supply line potential.

It is well known that each anode of an electron discharge device may carry current only when such anode is at a positive potential with respect Such flow of current may be prevented by maintaining a suitable control electrode associated with each anode at a potential below a so-called critical voltage which is generally approximately cathode potential. Such flow of current may, however, occur when the potential of the control electrode is not lower than such critical voltage because the blocking action of the control electrodes is variable dependent upon the conditions of pressure and of temperature within the device and upon the instantaneous voltage of the associated anode, and is frequently disturbed by the occurrence of socalled back fires during which the control electrode acts as a cathode to receive current from the cathode of the device which then operates as an anode. In addition, the current flowing through a control electrode must be limited by insertion of resistance in the circuit thereof with the result that the source of energization of the control electrode is only indirectly connected therewith so that the potential of the control electrode may easily difier by considerable amounts from the potential applied thereto from the source. The above disadvantages are particularly objectionable in direct current inverting systems in which the sequence of energization of the control electrodes must be very accurate. Such disadvantages may be obviated by maintaining the control electrodes at such a potential that no flow of current may occur from the anodes of the device when such anodes are energized at their normal operating voltages. Such flow of current may then be initiated by momentarily increasing the potential of each anode to such a value that the potential applied to the associated control electrode is no longer sufiicient to prevent picking up of the are by the anodes.

It is therefore among the objects of the present invention to provide a control system for electron discharge devices of the gaseous or of the vapor type whereby the flow of current through an anode cannot occur upon energization of such anode at the normal operating voltage thereof.

Another object of the present invention is to provide a control system for electron discharge devices of gaseous or of the vapor type whereby the flow of current through an anode may be initiated by means other than the control electrodes associated therewith.

Another object of the present invention is to provide a control system for electron discharge devices of gaseous or of the vapor type whereby the flow of current through an anode may be initiated only by momentary energization of such anode at a voltage higher than the normal operating voltage thereof.

Another object of the present invention is to provide a control system for electron discharge devices of gaseous or of the vapor type whereby the anodes of the device may sequentially receive voltages through auxiliary electron discharge devices to control flow of current through such devices.

Objects and advantages other than those above described will be apparent from the following description when read in connection with the accompanying drawing, in which:

Fig. l diagrammatically illustrates one embodiment of the present invention in which the anodes of a six-phase electron discharge device operable as an electric current rectifier may sequentially receive discharges from a condenser through the segments of a distributor to initiate the flow of current through the anodes, and in which the condenser is charged from a direct current source.

Fig. 2 partially illustrates a modified embodiment of the present invention differing from the embodiment illustrated in Fig. l in that the condenser may be charged from the supply line instead of from a direct current source. Fig. 3 partially illustrates a further modified embodiment of the present invention utilizing a plurality of condensers receiving their charges from an alternating current generator, and

Fig. 4 illustrates, partially in cross-section, one method of construction of the generator utilized in the embodiment illustrated in Fig. 3.

Referring more particularly to the drawing by characters of reference, reference numeral 6 designates an alternating current supply line herein illustrated as a three phase line for the reason that such type of line is most frequently utilized in practice. Line 6 energizes the delta connected primary winding 7 of a transformer having a secondary winding 8 comprising a plurality of portions such as 811 connected in star to form a neutral point. The different portions of winding 8 are severally connected, preferably througha plurality of reactors such as 11, with anodes, such as 12, of an electron discharge de- L10 vice 13 having a cathode 14. Electron discharge device 13 is herein shown as being of the metallic vapor arcing type and is assumed to be provided with the usual ignition and excitation means (not shown) Device 13 is assumed to be operable as an electric current rectifier and cathode 14 thereof is therefore connected with the positive conductor 16 of a direct current output circuit having the negative conductor 1'7 thereof connected with the neutral point of winding 8. Rectifier 13 is provided with a plurality of control electrodes such as 18 which may be severally energized through resistances such as 21 from a battery 19 connectedwith cathode- 14 of the rectifier. The construction of the control electrodes is assumed to be such, as is well known, that, while such control electrodes are energized from battery 19, current may not now through the anodes of the rectifier when such anodes are energized at their operating voltages, but may flow when suchanodes momentarily receive a voltage which is higher. than the normal operatingpeak voltage thereof.

Each anode 12 is connected with a discharge segment 22 of a: distributor 23 operating in synchronism with the voltage of line 6 and preferably driven by means of a synchronous motor 24 energized from line 6. Distributor 23 is provided. with a brush 25 which alternately comes in contact with one of; the discharge segments 22 of the distributor and withone of a plurality of charging segments26. The charging segments and the discharging. segments are equal in number to thenumber of. anodes of rectifier 13. The charging segments are connected with the positive terminal of a direct current source such as a generator 27- having the negative terminal thereof connected with cathode 14, and capable of supplying a voltage which is: considerably higher than thepeak' operating voltage of winding 8. It will be understood that generator 27 may be replaced by any suitable source of direct current such as afbattery or by a rectifying'system energized from line 6 or from another supply of alternating current. Brush 25 is connectedwith a condenser 28 through a resistance 29-to limit the rate of charge or of discharge of condenser 28 and thereby to limit the current in- .tensity within the members of distributor 23.

The. sequential connection of brush 25 with the different segments of distributor 23 may be adjusted with respect tothe voltage cycle of line 6 by spatially adjusting the position of such segments by means of a lever 31., Itwill be understood that distributor 23 may' be enclosed in vacuumor in a gas or a liquid under high pressure to improve the degree of insulation between the several segments thereof and to-reduceany arcing which might occur between. the segments and the brush.

In operation, assuming the system connected to be as shown on the drawing and line 6 to be energized, winding '7 is energized from line 6 with the result that winding 8 impresses six phase voltages in sequence on the several anodes of rectifier; 13. ,As stated above, it is assumed that/when the'control: electrodes of rectifier 13 are energized from battery 19 and the anodes of. the rectifiers; areenergized at their normal operating voltages from winding 8, no current may flowthrough the rectifier due to the block.- ing action of the control electrodes. Distributor 23: being operated by motor 24, the brush 25 thereofwill have contacted with segment 26. at aninstantprior to-the instant considered. Dur- .segment. former 32, .33 and distributor 23 constitute. a

ing such contacting period a circuit was established from generator 27 over segment 26, brush 25, resistance 29 and condenser 28 to charge condenser 28 at the voltage of generator 27. The rate of such charge is regulated by the value of resistance 29 and may be soadjusted that charging of condenser 28 is completed when brush 25 leaves segment 26 and the brush 25 leaves such segment without arcing. At the instant considered, brush 25 contacts with segment 22 thereby completing a circuit from condenser 28 over resistance 29, brush 25, segment 22 to anode 12 of the rectifier thereby impressing the voltage of condenser 28 between the anode 12 and the cathode 14 of rectifier 13 in open circuit. Such voltage is also impressed on a closed circuit comprising 'winding portion 8a, conductor 17, the

load connected therewith and conductor 16, but

due to the inductance of winding portion 8a such voltage remains impressed at substantially the fullvalue thereof between-anode 12 and cathode 14 on anode 12 for a sufiicient period of time to permit initiation of the flow of current from anode 12 to cathode 14. Current then flows from winding portion So over anode 12, cathode 1.4,.

conductors l6 and 17 to. the neutral .point of winding 8.as is well known in the art and such flow. of current continues as long as anode 12 is positive with respect to cathode. 14 and is no longer influenced by the-presence of control electrode 18 or by the potentialof generator 2'7. During such flow. of current, condenser 28is main,- tained. at a substantially.constantvoltage equal to the arc drop between anode 12 and cathode 14 so that brush 25 does not carry any current and may leave segment 22 without producing any arcing.

The above cycle of anode. energization is,re.- peated sequentially for each anode of rectifier 13 during each cycle of the voltage of line 6 to permit the flow of a substantially uniform current to the output circuitof rectifier 13. The moment in the voltage cycle of line 6 at which flow of current is initiated in anodel2- may be varied by adjustment of the segments of distributor 23 by means of lever 31, thereby also regulating the average voltage of the output circuit of the rectifier and the amount of current flowing therethrough.

In theembodiment illustrated in Fig.2 generator. 2'7 is omitted and the several charging segments 26 of. distributor 23 are severally con.- nected with the star connected portions 3311,- etc. of the, secondary winding 33 of a transformer having a primary winding 32 energized from line 6. The connections between winding 33 of the charging segments are such thatwinding 33 impresses an alternating potential on each char-g.- ing segment which potential is at substantially the maximum positive value thereof during the period when brush 25 is in contact with such It will, therefore, appear that transmechanicalrectifying system tending to maintain condenser 28 charged at a voltage equal to substantially the maximum value of the phase voltage of winding 33. j

The operation of the present embodiment. is

similar tothatofthe embodiment illustrated in Fig. 1 except in the'method of charging condenser 28. When brush 25' is in contactwith lib charging segment 26, a circuitis completed'from winding portion 33a over segment 26, brush 25, resistance 29 and condenser 28 bacl'rto the neutral point of. winding 33 whereby condenser 28 becomeschargedat the Voltage impressed thereon by winding portion 33a. 'The current taken by condenser 28 during such period first increases and then decreases and tends to reverse its direction when the voltage of winding portion 33a reaches the maximum value thereof. Distributor 23 is preferably so adjusted that brush 25 leaves segment 26 at the instant of reversal of current to interrupt the charging circuit without arcing. The discharge of the condenser over anode 12 occurs as described for the embodiment illustrated in Fig. 1.

In the embodiment illustrated in Fig. 3 each anode 12 of rectifier 13 is connected with a condenser 34 through discharge device 36 operable for conducting current in one direction only and only upon application thereon of a potential higher than the peak operating voltage of the section of winding 8, connected therewith. Such a device may be an asymmetrical spark gap or an asymmetrical glow tube or any equivalent device known in the art. Each condenser 34 is connected with a winding 37 of a generator 38 driven by synchronous motor 24 and replacing distributor 23 utilized in the previously described embodiments. Windings 37 are wound on cores 39 constituting an incomplete magnetic circuit therefor and carrying exciting windings 41. The several exciting windings of generator 38 may be connected in series and excited from a common source of direct current such as a battery 42. The several cores of generator 38 are assembled on a frame 43 which may be spatially adjusted by means of lever 31 and which constitutes a bearing for the rotor 44 of the generator. Rotor 44. carries a. camlike projection or pole piece 46 which sequentially bridges the air gaps of the several cores 39.

'In operation, considering the system at an instant at which it is desired to permit anode 12 to carry current as described with respect to the embodiment of Fig. l, lever 31 is so adjusted that, at the instant considered, pole piece 46 momentarily bridges the magnetic circuit of the core marked 39. The resulting changes in the magnetic flux flowing within core 39 cause the production, within winding 37, of a positive voltage impulse followed by a negative impulse. The positive impulse gradually charges condenser 34 up to the voltage at which device 36 breaks down and the voltage of condenser 34 is then impressed, through device 36, on the circuit receiving the voltage of condenser 28 as described in relation to the embodiments of Figs. 1 and 2 and with the results described relative to the operation of such embodiments.

The negative voltage impulse impressed on condenser 34 immediately thereafter results only in the charge of such condenser at the voltage of such impulse and is followed by the discharge of condenser 34 over winding 3'7.

Although but a few of the embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. In a control system for an electron discharge device, an alternating current line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes being connected with said line and the control electrodes being arranged to prevent flow of current from the anodes at the operating potentials supplied thereto from said line, a condenser connected with the cathode and arranged to be connected with the anodes of said device to apply potential surges thereto to initiate operation thereof, means for charging said condenser, and means for alternately connecting said condenser with said charging means and sequentially with said anodes.

2. In a control system for an electron discharge device, an alternating current line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes being connected with said line and the control electrodes being arranged to prevent flow of current from the anodes at the operating potentials supplied thereto from said line, a condenser connected with the cathode and arranged to be connected with the anodes of said device to apply potential surges thereto to initiate operation thereof, means for charging said condenser, means for alternately connecting said condenser with said charging means and sequentially with said anodes, and means operating in synchronism with the frequency of said line to operate the second said means for controlling said condenser.

23. In a control system for an electron discharge device, an alternating current line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes being connected with said line and the control electrodes being arranged to prevent flow of current from the anodes at the operating potentials supplied thereto from said line, a condenser connected with the cathode and arranged to be connected with the anodes of said device to apply potential surges thereto to initiate operation thereof, means for charging said condenser, means for alternately connecting said condenser with said charging means and sequentially with said anodes, said means being adjustable to vary the moments of connection of said condenser with said charging means and with said anodes to thereby control the periods of charging and discharging said condenser relative to the voltage cycle in said line, and means operating in synchronism with the frequency of said line to operate said means for controlling said condenser.

4. In a control system for an electron discharge device, an alternating current line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes being connected with said line and the control electrodes being arranged to prevent flow of current from the anodes at the operating potentials supplied thereto from said line, a condenser connected with the cathode and arranged to be connected with the anodes of said device to apply potential surges thereto to initiate operation thereof, means for charging said condenser, a distributor having contacts severally connected with th anodes of said device and contacts interposed between the first said contacts severally connected with said chrging means and a brush connected with said condenser and movable into engagement with successive ones or" said contacts to thereby control the alternate connection of said condenser with said charging means and sequentially with said anodes for charging and discharging of said condenser, and means for moving the brush of said distributor to and from connection with the successive ones of said contacts.

5. In a control system for an electron discharge device, an alternatin current line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes being connected with said line and the control electrodes being arranged to pr vent flow or current from the anodes at the operating potentials supplied thereto from said line, a condenser connected with the cathode and arranged to be connectedwith the anodes of said device to apply potential surges thereto to initiate operation thereof, means for charging said condenser, a distributor having segments severally connected with the anodes of said device and segments alternating with the first said segments severally connected with said charging means and a brush connected with said condenser and rotatable into engagement with the segments to thereby control the alternate charging and discharging of said condenser sequentially through said anodes, and a motor connected with said. line to rotate the brush of said distributor.

6. In a control system for an electron discharge device, an alternating current line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes being connected with said line and the control electrodes being arranged to prevent flow of current from the anodes at the operating potentials supplied thereto from said line, a condenser connected with the cathode and arranged to be connected with the anodes of said device to apply potential surges thereto to initiate operation thereof, means for charging said condenser, a distributor having segments severally connected with the anodes of said device and segments interposed between the first said segments connected with said charging means and a brush connected with said, condenser and rotatable into engagement with the successive segments to thereby control the alternate charging and discharging of said condenser sequentially through said anodes, the relative positions of the segments and the brush of said distributor being variable to vary the time of charging and discharging of said condenser relative to the potential cycle in said line, and a motor connected with said line to rotatethe brush of said distributor.

'7. In a control system for an electron discharge device, an alternating current line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes'being connected with said line and the control electrodes being arranged. to prevent how of current from the anodes at the operating potentials supplied thereto from said line, a condenser connected with the cathode and arranged to be connected with the anodes of said device to apply potential surges thereto to initiate operation thereof, a source of direct current connected with the cathode of said device, a distributor having segments severally connected with the anodes of said device and having segments interposed between the first said segments severally connected with said source and having a brush connected with said condenser and rotatable into engagement with successive ones of said segments to thereby control the alternate charging and discharging of said condenser sequentially through said anodes, and a motor connected with said line to rotate the brush of said distributor.

8. In a control system for an electron discharge device, an alternating current'line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes being connected with said line and the control electrodes being arranged to prevent flow of current from the anodes at the operating potentials supplied thereto from said line, a condenser connected with the cathode and arranged to be connected with the anodes 'of said device to apply potential surges thereto to initiate operation thereof, atransformer connected with said line and'having a polyphase secondary winding,'a dis tributor having segments severally connected with the anodes of said device and segments interposed between the first said segments severally connected with the phases of the secondary winding of said transformer and a brush connected with said condenserand rotatable into engagement with the successive ones of said segments to thereby' control charging and discharging of said condenser sequentially through said anodes, and a motor connected with said line to rotate the brush of said distributor.

9. In a control system for an electron discharge device, an alternating current line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes being connected with said line, asource of potential negative relative to the potential of the cathode of said device, the control electrodes of said device being continuously connected with said source to prevent operation of the anodes thereof at the operating potentials applied thereto from said line, a condenser arranged to be connected with the anodes of said device to apply potential surges thereto higher than the operating potentials to initiate operation thereof, means for charging said condenser, and means for controlling the alternate charging and discharging of said condenser sequentially through said anodes.

10. In a control system for an electron discharge device', an alternating current line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes being connected with said line,'a source of potential negative relative to the potential of the cathode of said device, the control electrodes of said device being continuously connected with said source toprevent operation of the anodes thereof at the operating potentials applied thereto from said line, a condenser arranged to be connected with the anodes or said device to apply potential surges thereto higher than the operating potentials to initiate operation thereof, means for charging said condenser, a distributor having segments severally connected with the anodes of said device and segments interposed between the first said segments severally connected with said charging means and a brush connected with said condenser and rotatable into engagement with successive ones of the segments tocontrol the alternate charging and discharging of'said condenser by way of said anodes, the relative positions of the segments and the brush of said distributor being variable to vary the moments of charging and discharging of said condenser relative to the potential cycle of said line, and a motor connected with said line to rotate the brush of said distributor. V

11. In a control system for an electron discharge device, an alternating current line, an electron discharge device having anodes with associated control electrodes, the anodes being connected with said line and the control electrodes being arranged to prevent flowof current'from the anodes at'the operating potentials supplied thereto from said line, a plurality of condensers connected'with thecathcde of said device,.means permitting only unidirectional flow of current for sequentially connecting said condensers severally with the anodes of said device, av generator for charging said condensers, and means connected with said line for operating said generator.

12. In a control system for an electron discharge device, an alternating current line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes being connected with said line, a source of potential negative relative to the potential of the cathode of said device, the control electrodes of said device being continuously connected with said source to prevent operation of the anodes thereof at the operating potentials applied thereto from said line, a plurality of condensers connected with the cathode of said device, means permitting only unidirectional flow or" current for sequentially connecting said condensers severally with the anodes of said device, a generator for charging said condensers, and means connected with said line for operating said generator in synchronism with the frequency of said line.

13. In a control system for an electron discharge device, an alternating current line, an electron discharge device having anodes with associated control electrodes, the anodes being connected with said line and the control electrodes being arranged to prevent flow of current from the anodes at the operating potentials supplied thereto from said line, a plurality of condensers connected with the cathode of said device, means permitting only unidirectional flow of current above a predetermined potential for sequentially connecting said condensers severally with the anodes of said device to control the discharging of said condensers therethrough, a generator for charging said condensers, means connected with said line for operating said generator, and means for varying the phases of the output potentials of said generator relative to the phases of the potentials in said line.

14. In control apparatus for vacuum electric apparatus such as rectifiers, inverted rectifiers and the like, the combination of an evacuated envelope housing a cathode and a plurality of anodes, and an alternating current network connecting said cathode and anodes to establish in phase sequence on said anodes positive potentials less than the ignition potential required to initiate current flow to said anodes and of a magnitude effective to maintain such current flow after the initiation thereof, of means operative independently of current how in said network for momentarily establishing on said anodes and in phase sequence an overvoltage which raises the anode potential momentarily above the ignition potential; said means comprising a source of direct current potential, a condenser, and means including a distributor switch for alternately charging said condenser from said source and discharging the same in phase sequence through circuits including said cathode and the respective anodes.

15. Control apparatus as claimed in claim 14, 100 wherein said switch is a rotary distributor switch having alternately arranged charging and discharging contacts, said discharging contacts being connected to the respective anodes, a contact for said switch alternately engaging a charging con- 1G5 tact thereof to complete a circuit including said source of potential and said condenser and then a discharging contact to complete a circuit including the charged condenser and one of said anodes.

ERNST KOBEL. 

